Lactobacilli rank among lactic acid bacteria, fermenting saccharides to produce lactic acid. The individual species and strains differ by the profiles of fermented saccharides, but this property is not sufficient for the identification at the species level. The species and strains differ in the 16S rDNA sequence and in the intergenic space between 16S and 23S rDNA, which make their differentiation and identification possible. Some representatives of the genus Lactobacillus are included in probiotic preparations with regard to their beneficial health effects on the human and animal organisms. For example, they are able to interact with the immune system and stimulate it positively, to reduce the manifestations of lactose intolerance by consuming fermented milk products, and to shorten postantibiotic and travellers’ diarrhoea. Lactobacilli also produce bacteriocins, antimicrobially active substances.

        Key words: Lactobacillus – probiotics – bacteriocins – bacteria of lactic fermentation – 16S rDNA